首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2238篇
  免费   8篇
电工技术   6篇
化学工业   52篇
金属工艺   12篇
机械仪表   4篇
建筑科学   13篇
能源动力   2篇
轻工业   40篇
水利工程   3篇
石油天然气   1篇
无线电   22篇
一般工业技术   42篇
冶金工业   2026篇
原子能技术   1篇
自动化技术   22篇
  2021年   6篇
  2020年   4篇
  2019年   2篇
  2018年   3篇
  2017年   2篇
  2016年   6篇
  2015年   4篇
  2014年   5篇
  2013年   15篇
  2012年   11篇
  2011年   17篇
  2010年   14篇
  2009年   7篇
  2008年   6篇
  2007年   8篇
  2006年   9篇
  2005年   11篇
  2004年   8篇
  2003年   11篇
  2002年   3篇
  2001年   5篇
  2000年   7篇
  1999年   75篇
  1998年   723篇
  1997年   395篇
  1996年   238篇
  1995年   124篇
  1994年   119篇
  1993年   120篇
  1992年   19篇
  1991年   24篇
  1990年   9篇
  1989年   20篇
  1988年   14篇
  1987年   16篇
  1986年   10篇
  1985年   17篇
  1984年   2篇
  1983年   4篇
  1982年   3篇
  1981年   11篇
  1980年   13篇
  1978年   2篇
  1977年   32篇
  1976年   71篇
  1975年   4篇
  1970年   3篇
  1930年   1篇
  1928年   1篇
  1927年   1篇
排序方式: 共有2246条查询结果,搜索用时 15 毫秒
81.
We estimated the variability among nations in the prevalence of stunting and wasting, evaluated which national factors are associated with stunting and wasting and examined the relationship of stunting with wasting. The World Health Organization Global Database on Child Growth, a comprehensive conceptual model and a database of national factors were used with variance components and regression analyses. There was substantial variability among nations and among provinces within nations. Most national variability for stunting (76%) and wasting (66%) was explained by national factors and geographic region. Higher energy availability, female literacy and gross product were the most important factors associated with lower prevalence of stunting. The association of health expenditures and stunting differed by region. Higher immunization rate and, for Asia only, energy availability were the most important factors associated with lower prevalence of wasting. Regional differences in the relationship between stunting and wasting were accounted for by national factors. Some factors associated with stunting and wasting differ at the national level. Child malnutrition within a household is greatly influenced by issues at national and provincial levels, and intervention should be considered at all three levels.  相似文献   
82.
83.
84.
Thirty-one right-hemisphere lesioned (RHL) patients, 11 left-hemisphere lesioned patients (LHL) and 10 normal controls (NC) bisected lines in three spatial location and four directional cuing conditions. The error direction and error size were analyzed as separate and combined variables. Seventy-seven percent of RHL patients and 45% of LHL patients made abnormally large errors in line bisection. Right-hemisphere lesioned patients were more sensitive to spatial location and directional cuing than NC subjects. In contrast, LHL patients were less sensitive to either condition than NCs. The error direction and error size emerged as dissociable components of line bisection. Right-hemisphere lesioned patients and NC subjects bisected lines consistently to one side of the true center. Left-hemisphere lesioned patients bisected lines equally often on both sides of the true center. Both RHL and LHL patients made larger absolute bisection errors than NC subjects, but the RHL patient's errors were larger than those of the LHL patients. We propose that the greater sensitivity of RHL patients to spatial location and directional cues and the directional consistency of their bisection errors represent contributions of the intact left cerebral hemisphere to line bisection. In contrast, the LHL patient's unrestrained ability to orient to both ends of the line reflects a contribution of the intact right cerebral hemisphere to line bisection. The failure of both groups to accurately bisect lines reflects a common visuospatial processing deficit that is more pronounced following RHLs than LHLs.  相似文献   
85.
OBJECTIVE: To evaluate the ocular toxicity of intravitreous octreotide. DESIGN: New Zealand white rabbits weighing approximately 2 kg were given 5 mg (group 1, two eyes), 2 mg (group 2, four eyes), 1 mg (group 3, four eyes), 0.5 mg (group 4, two eyes), 0.3 mg (group 5, two eyes) or 0.1 mg (group 7, two eyes) of octreotide acetate, two doses of 0.3 mg 1 week apart (group 6, four eyes) or 0.1 mL of balanced salt solution (group 8 [control group], two eyes). OUTCOME MEASURES: Findings on clinical examination and electroretinography, performed before and 10 days after injection, and on light microscopy. RESULTS: Cataracts developed in groups 1 and 2. No clinical changes were found in groups 3 to 8. Electroretinography showed various degrees of decrease in the b-wave amplitude in groups 1 and 2; the results were normal in groups 3 to 8. Histologic examination showed macrophage and monocyte infiltration in the vitreous and retina in group 1. No histologic change was seen in the eyes in groups 2 to 8. CONCLUSIONS: Octreotide injected intravitreally is safe at dosages of 1 mg or less.  相似文献   
86.
87.
BACKGROUND/AIMS: Malignancy is known to be associated with hepatolithiasis. The present report summarizes the results of our management of patients with cholangiocarcinoma associated with hepatolithiasis. MATERIALS AND METHODS: Twenty patients with cholangiocarcinoma and associated hepatolithiasis were analyzed retrospectively. There were 12 males and 8 females, with a mean age of 59.3 years. The clinical records of these patients were reviewed to determine demographic characteristics, clinical features, laboratory findings, diagnostic tests, operative management and results of therapy. RESULTS: One patient was moribund on presentation and was treated conservatively. Fourteen patients underwent hepatic resection. Three of them had palliative resection. Hepatic resection was less likely to be performed in patients having right lobe disease (50%) as compared to patients having left lobe disease (90%) (p = NS). The overall operative morbidity and mortality rates after hepatic resection were 36% and 7%, respectively. Non-resective operations were performed in five patients. The overall operative morbidity and mortality rates after non-resective operations were 20% and 0%, respectively. After curative hepatic resection (11 patients), the 1- and 2-year survival rates were 81% and 51%, respectively. CONCLUSIONS: A suspicion of malignancy is necessary in managing patients with hepatolithiasis. Hepatic resection is the treatment of choice for cholangiocarcinoma when it is resectable.  相似文献   
88.
89.
Previous studies have suggested that multidrug resistance (MDR) reversal by polyoxyethylene surfactants involves alterations in plasma membrane lipid physical state of resistant cells as one of the possible mechanism(s). To date, however, a detailed and critical examination of the relationship between membrane lipid fluidity and MDR reversal by these surfactants has not been performed. In the present studies, therefore, a series of experiments were conducted to critically examine the role of membrane lipid physical state in MDR reversal by employing a unique class of clinically important nontoxic lipophilic surfactants and the KB-8-5-11 drug-resistant cell line. MDR reversal was assessed by rhodamine-123 uptake. The effect of surfactants on plasma membrane lipid fluidity of these cells was assessed utilizing a fluorescence polarization technique with fluorophores DPH, TMA. DPH, 2-AS, and 12-AS. Our studies demonstrated that: (i) in vitro addition of active MDR-reversing surfactants (Solutol HS-15, Tween 40, and Cremophor EL, 10 micrograms/ml each) decreased lipid fluidity of isolated crude plasma membranes of resistant cells; (ii) the inactive surfactants (octylglucoside, hecameg) failed to influence membrane lipid fluidity; (iii) cells grown in the presence of active surfactants also exhibited a decreased plasma membrane lipid fluidity as measured with intact cells utilizing the probe TMA.DPH; and (iv) active surfactants did not influence lifetimes of the excited state of the fluorophores. These findings demonstrate that decrease of the plasma membrane lipid fluidity of KB 8-5-11 resistant cells may be one of the important mechanism(s) of MDR reversal by polyoxyethylene surfactants.  相似文献   
90.
Methods for the interpretation of veterinary clinical biochemistry have not developed as rapidly as biochemical technology. However, the results of clinical biochemistry tests are only of value when they are interpreted appropriately. A retrospective study was undertaken to investigate the equine biochemistry data which had been stored in a veterinary hospital database. By applying percentile analysis and Bayesian probability methods to the clinical biochemistry and corresponding diagnosis data, a novel method for the interpretation of clinical biochemistry data has been developed. The method allows clinicians to determine whether a biochemistry value is abnormal, its degree of abnormality, and the most likely associated diagnoses. The method could be used to investigate a practice-based population and may have significant implications for the interpretation of clinical biochemistry data in veterinary medicine in the future.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号